The long-range goals of this research project are: 1) to determine the exact structure of the major structural protein of the type C retrovirus RNP-complex and its function in the packaging of viral RNA; and 2) to determine the chemical structures of the avian oncornavirus surface glycoprotein, gp85, responsible for type specific antigenic properties and for specific viral attachment to target cells. Studies during the coming year will concentrate on: 1) completing the determination of the amino acid sequence of PR-RSV-C p12 well in progress; 2) determining which 2 of the 6 half-cystinyl residues of PR-RSV-C p12 are linked by disulfide bond; 3) partial sequence analysis of selected peptides from AMV p12 to complete comparison of the sequences of AMV and PR-RSV-C p12s; 4) comparison of the cyanogen bromide and cysteinyl cleavage fragments of a number of avian oncornavirus p12s by gel electrophoretic methods to examine in particular, similarities in the amino and carboxyl terminal sequences; 5) to examine the oligomeric structure of p12 bound to RNA by x-ray crystallographic studies; and 7) to investigate more fully the role of both the carbohydrate and polypeptide moieties of avian oncornavirus gp85s in determining their antigenic properties.